These words refer to statements that are simple, direct or forceful, or to a guileless or tactless manner. While outspoken applies approvingly to vigorous statements of one’s position or sentiments, it can also suggest a brusque manner or an indifference to the feelings of others. In any case, it is the strongest word here, carrying overtones of fearlessness and aggressiveness, as well: an outspoken critic of the automotive industry’s standards of car safety; an outspoken fool who blustered and stormed but never got his facts right. Used in a more general way, the word can indicate, with greater neutrality, a willingness to take a stand or express oneself: He urged the timid boy to be a little more outspoken about his needs and desires.

Where outspoken often implies criticism of others, open often suggests someone’s willingness to expose himself and his vulnerabilities to another person: successful marriages in which both partners are open with each other. The word can also refer more specifically to an unthinking or fearless lack of secrecy, particularly in its adverbial form: They carried on their affair quite openly , without shame or guilt. The word can also apply to whatever is widely known, or to public statements deliberately made for the record: an open secret; an open scandal; an open avowal of their intention to compete for the government contract. By extension, the word can indicate whatever is tantamount to a direct or public acknowledgement: She gave me a smile that was an open admission of her contempt for our immediate superior.

Straightforward most often applies to a character trait; it indicates a lack of deviousness in the way someone deals with other people. While it suggests unflinching directness in making requests of others, it does not need to suggest either a lack of consideration, as is possible for outspoken , or a willingness to be exposed and vulnerable, like open : a courteous but straightforward refusal to give me the facts about his past. Forthright is more closely related to open in suggesting either a readiness to respond to the request of others or a sincere statement that does not hedge or involve evasion: a forthright person, always willing to give his dissatisfaction with his own work on the town-planning project.

Plain-spoken is like straightforward in indicating directness, but adds to this implications of simple and unambiguous utterance, as well: She replied to their complex reasons and arguments with a plain-spoken refusal to co-operate. The word can even function more emphatically to indicate a terse or blunt statement that completely rejects circumlocutions and euphemisms: He argued that it was merely being honest and plain-spoken to speak about starvation where these native villagers were concerned, and not about food shortages, hunger or malnutrition.